Thanks, Gord! That did the trick. If anyone else needs this fix, here it is...
To programatically reset the used range,
Sub DeleteUnused()
Dim myLastRow As Long
Dim myLastCol As Long
Dim wks As Worksheet
Dim dummyRng As Range
For Each wks In ActiveWorkbook.Worksheets
With wks
myLastRow = 0
myLastCol = 0
Set dummyRng = .UsedRange
On Error Resume Next
myLastRow = _
.Cells.Find("*", after:=.Cells(1), _
LookIn:=xlFormulas, lookat:=xlWhole, _
searchdirection:=xlPrevious, _
searchorder:=xlByRows).Row
myLastCol = _
.Cells.Find("*", after:=.Cells(1), _
LookIn:=xlFormulas, lookat:=xlWhole, _
searchdirection:=xlPrevious, _
searchorder:=xlByColumns).Column
On Error GoTo 0
If myLastRow * myLastCol = 0 Then
.Columns.Delete
Else
.Range(.Cells(myLastRow + 1, 1), _
.Cells(.Rows.Count, 1)).EntireRow.Delete
.Range(.Cells(1, myLastCol + 1), _
.Cells(1, .Columns.Count)).EntireColumn.Delete
End If
End With
Next wks
End Sub